1. Field of the Invention
The present invention relates to write driver circuits for magnetic recording. More particularly, the present invention relates to write driver circuits for high data rate magnetic recording and techniques for fabricating such write driver circuits.
2. Description of the Related Art
FIG. 1 shows a high RPM disk drive 10 having a magnetic read/write head (or a recording slider) that is positioned over a selected track on a magnetic disk 11 for recording data using a servo system. The stage servo system includes a voice-coil motor (VCM) 13 for coarse positioning a read/write head suspension 12 and may include a microactuator, or micropositioner, for fine positioning the read/write head over the selected track. FIG. 2 shows an enlarged exploded view of the read/write head end of suspension 12 in the case when a microactuator is also being used. An electrostatic rotary microactuator 14 is attached to a gimbal structure 15 on suspension 12, and a slider 16 is attached to the microactuator. A read/write head 17 is fabricated as part of slider 16.
For high data rate magnetic recording, the write path of a recording channel front-end requires a wide bandwidth and short waveform rise and fall times in order to accurately transfer high-frequency write data patterns to a magnetic medium) such as a disk. The virite signal includes abrupt switching, that is, polarity reversals of the signal, that represent the information that is to-be-recorded. The abrupt switching generates high-frequency harmonics that must be transferred from the write driver to the magnetic write transducer (write head) in order that the write signal is accurately transferred onto the magnetic medium.
Conventional write drivers have a high output impedance, essentially forming a current source for the write current needed to drive an inductive write head. The output impedance is much greater than the head input impedance. FIG. 3 shows a conventional write driver circuit 30 that is connected directly to the (bonding) terminals of a magnetic write transducer (write head) 32 through a suspension interconnect 31. Write driver circuit 30 is configured as a current commutating write-driver circuit and includes two switches S and two switches S that are connected in an H configuration. An obstacle in transferring the write data output signal from write driver circuit 30 to write head 32 is in the propagation of the write signal along interconnect 31 between write driver circuit 30 and the write head 32.
The invention described below improves the propagation of the write signal along an interconnect between a write driver circuit and a write head, while maintaining the signal integrity, i.e., the signal properties essential for high data rate writing.